The current IDEC Pharmaceuticals protocol evaluating the efficacy and safety of IDEC-Y2B8 is a randomized study comparing Rituxan alone to Rituxan and radiolabelled monoclonal antibody therapy. It is restricted to patients who have platelet counts above 150,000. The proposed study IDEC 106-05 is a non-randomized study using Rituxan and IDEC Y2B8 for patients with platelet counts from 100-150,000.